At present, plate heat exchangers are often used in the media condensing, evaporating and mutual heat exchange processes. The heat exchange plates forming the plate heat exchangers are usually connected and sealed by welding or brazing and the use of adhesives or sealing gaskets between the plates.
In SE-B-415928, a plate heat exchanger comprising many heat exchange plates was announced, in which each heat exchange plate comprises the first end zone with the first and second corner holes, the second end zone and the central heat exchange zone extending from the first end zone to the second end zone, and the central heat exchange zone is corrugated; the corner holes as the inlet and outlet of the same fluid are located on the same side of the heat exchange plate.
In WO85/02670, a plate heat exchanger consisting of many heat exchange plates was announced, in which each heat exchange plate comprises the first end zone with the first and second corner holes, the second end zone and the central heat exchange zone extending from the first end zone to the second end zone, and the central heat exchange zone is corrugated; the central heat exchange zone extends from first end zone to second end zone; the said corner holes used as the inlet and outlet of the same fluid are located on the same side of the heat exchange plate; the first distribution zone extends in the first end zone, and the second distribution zone extends in the second end zone; in the said distribution zones there are some convexes arranged in a regular order, and because of these convexes, the flow resistance of heat exchange media in the gap between distribution zones is less than that in the gap between plates in the central heat exchange zone.
The deficiency of the above-mentioned plate heat exchanger is: when the heat exchange plates are arranged by stacking with each other and connected and sealed together, the support between the central heat exchange zone of each layer and the mechanical resistance to working pressure depends on the limited mutual contact points between the corrugated ridge lines and the property of the connecting substance between the contact points, and the shape, quantity and distribution status of these contact points depend not only on the need to satisfy the heat exchange media, but also on the mechanical performance of the materials used to make the heat exchange plates. If some materials are relatively weak but must be used for their special properties, or materials with relatively low mechanical performance are used to make heat exchange plates, and when some connecting and sealing materials with special properties have to be used, the service requirements may not be met in resistance against rupture pressure and anti-fatigue life in this type of plate heat exchangers because of insufficient contact points formed by corrugated elements between the central heat exchange zones.
Another deficiency of this type of plate heat exchanger is: each corrugated central heat exchange zone on each heat exchange plate is made with fixed die set by hydraulic forming, and after completion of fabrication with die set, the corrugation distribution on the central heat exchange zone in the heat exchange plate cannot be changed, therefore, heat exchange can be realized only with the central heat exchange zone of the same corrugation distribution even when different heat exchange media are used. Therefore, in the present manufacture of plate heat exchangers, heat exchange plates with central heat exchange zones of different corrugation distribution are made to meet requirements for different heat exchange media, which however will increase the manufacture cost of products.